Directions

Combine the potatoes and leeks on a sheet pan in a single layer. Add the olive oil, 1 teaspoon salt, and 1/2 teaspoon pepper and toss to coat the vegetables evenly. Roast for 40 to 45 minutes, turning them with a spatula a few times during cooking, until very tender. Add the arugula and toss to combine. Roast for 4 to 5 more minutes, until the arugula is wilted. Remove the pan from the oven and place over 2 burners. Stir in the wine and 1 cup of the chicken stock and cook over low heat, scraping up any crispy roasted bits sticking to the pan.

In batches, transfer the roasted vegetables to a food processor fitted with the steel blade, adding the pan liquid and about 5 cups of the chicken stock to make a puree. Pour the puree into a large pot or Dutch oven. Continue to puree the vegetables in batches until they're all done and combined in the large pot. Add enough of the remaining 1 to 2 cups of stock to make a thick soup. Add the cream, creme fraiche, 2 teaspoons salt, and 1 teaspoon pepper and check the seasonings.

When ready to serve, reheat the soup gently and whisk in 2 tablespoons white wine and 1/4 cup of Parmesan. Serve hot with an extra grating of Parmesan and crispy shallots, if using.

Reduce the heat to low, add the shallots, and cook for 30 to 40 minutes, until they are a rich golden brown. The temperature should stay below 260 degrees F. Stir the shallots occasionally to make sure they brown evenly. Remove them from the oil with a slotted spoon, drain well, and spread out to cool on paper towels. Once they have dried and crisped, they can be stored at room temperature, covered, for several days.